Hard disk drives (HDD) have been increasing the recording density of the magnetic disks on which data storage occurs. Correspondingly, the thin-film magnetic heads used to write and read that data have been required to improve their performance as well. The thin-film read/write heads most commonly in use are of a composite type, having a structure in which a magnetic-field detecting device, such as a giant-magnetoresistive (GMR) read sensor is used together with a magnetic recording device, such as an electromagnetic coil inductive device. These two types of devices are laminated together and mounted on a rectangular solid prism-shaped device called a slider. The slider literally flies over the rotating surface of the disk being held aloft by aerodynamic forces at a height called the fly height (FH). The read/write head is mounted in the slider where it serves to read and write data signals, respectively, from/onto magnetic disks which are the usual magnetic recording media in a HDD. The magnetic writer portion of the read/write head is a small electrically activated coil that induces a magnetic field in a pole. The field, in turn, emerges at a narrow write gap (WG) and can change the direction of the magnetic moments of small magnetic particles, or groups of particles, embedded in the surface of the disk. If the embedded particles are embedded in such a way that their moments are perpendicular to the disk surface and can be switched up and down relative to the plane of that surface, then you have what is called perpendicular magnetic recording (PMR). The perpendicular arrangement produces a more densely packed region for magnetic recording.
Perpendicular magnetic recording (PMR) heads, which record in a direction perpendicular to the plane of the recording media, have made it possible to extend the ongoing increase in the recording density of hard disk drives (HDD) beyond 100 Gb/in2. However, even using PMR heads, it is difficult to extend the density beyond 1 Tb/in2 due to thermal stability of the media and the media's super-paramagnetic limit. In order to achieve a higher recording density, a new technology has been developed: Thermally Assisted Magnetic Recording (TAMR). Briefly, the media that can be effectively used to record at these ultra-high densities must have extremely high coercivities so that data, once it is recorded, can remain stable even when subjected to thermal effects. Unfortunately, the high coercivities required to maintain the data once it is recorded, also makes it difficult for the limited flux densities of the small PMR heads to actually create magnetic transitions and record that data into the media. One way to do this, is to heat the recording media during the actual recording process so that its coercivity is temporarily reduced and then to record the data on the heated surface. When the surface cools, the coercivity is restored to its ambient value and the recorded data becomes stable.
As is well known, a typical TAMR head is a read/write head (a slider-mounted PMR head in the present case) that is furnished with: (1) a Laser diode to provide optical thermal energy via optical radiation, (2) an optical waveguide to transfer that radiation close to the recording surface, and (3) a plasmon generator located near that surface. The plasmon generator is a device that receives the optical radiation, converts it, by electromagnetic coupling to the excitation of plasmon modes and then transfers energy from the plasmon near-fields to a region of the recording media. The near-fields, not being radiative, are not subject to diffraction effects and can be highly localized. The localized near-field energy appears as a near-field spot at the tip of the plasmon generator's air bearing surface (ABS). This tiny near field spot emerges at the ABS of the PMR read/write head adjacent to the emerging magnetic pole tip of the write portion of the PMR. During write operations, the emerging near-field spot induces a very localized temperature rise in the recording media to assist magnetic writing. At the same time, the near-field energy induces a very sharp or localized thermally-induced protrusion on the recording head that causes many issues that should be dealt with. Note that this disclosure will address the read/write head and not provide any additional description of these TAMR components that produce the near-field spot as they are now well known in the field and features of the TAMR head, where the near-field energy is deposited and the read/write operations occur.